Agricultural mixers are used for mixing hay and silage together with other nutrients including animal feed supplements and grains. These feed materials are then discharged and fed to various livestock such as cattle and dairy cows. Sometimes the mixing of such feed includes depositing a whole round or square bale of hay into the mixer. The mixer then cuts and processes the bale into the desired consistency before and during the mixing of the other feed nutrients.
In known mixers, there are many different configurations including horizontal augers, reel type arrangements, and vertical augers. In the vertical auger type mixers, there are single auger designs and multiple auger designs. In multiple auger vertical mixers, each auger is typically driven using a right-angle gearbox of either helical gear or planetary type construction. The gearboxes are normally driven by a single PTO driveline from the tractor or truck, which turns at approximately 1000 RPM. This drive input is attached to the input shaft of the first gearbox, which drives two output shafts, one right angle output for the first auger, the other straight through for the second gearbox. A second driveline is attached to the straight through output shaft of the first gearbox and is connected to the input shaft of the second gearbox, which then drives the second auger.
A torque limiting device is typically installed before the first gearbox, to protect the entire drive system from overload. The torque disconnect device can be a ball type torque disconnect, slip clutch, shear pin, belt drive or other commonly used method of drive protection.
It is understood that the term “gearbox” is used as a generic description for a means of transferring torque, and could also be a chain or belt driven device without changing the intended function.
One disadvantage of having the PTO driveline attaching directly to the first gearbox is that the speed reduction required to slow the drive from 1000 RPM to approximately 36 RPM is significant, and often requires the use of an expensive planetary gearbox.
Another disadvantage of this drive arrangement is that the single torque limiting device must be sized to handle the full combined running load of the mixer. If one of the augers gets jammed, the torque on that one gearbox can easily exceed the gearbox capacity, without exceeding the rating of the torque limiting device. For example, a single torque limiting device might be set for 2.5 times the combined normal running load of the augers, which then exceeds the breaking strength of one single gearbox. If one auger became jammed, it would likely break the gearbox before the single torque limiting device would disengage. This disadvantage becomes even more pronounced when adding a third or additional augers operating on a single torque disconnect system.
Yet another disadvantage of this arrangement is that the drive protection is exactly the same for all augers, even though the needed torque for each auger may be unique.